1. Field of the Invention
The present invention relates to a process and installation for composting waste material comprising organic matter, in particular but not exclusively municipal waste including household, commercial and industrial waste. The process and installation according to the instant invention also provides for sorting the non-organic recyclables present in the household, commercial and industrial waste.
2. Brief Description of the Prior Art
With the increase in urbanization and the advancement of the consuming society there has been a rapid increase in waste. The traditional way of disposing of this waste has been dumping it into landfill sites. Since most of the landfill sites are not sufficiently secure to prevent contamination of ground water and pollution of air by landfill produced methane, landfill sites have become an environmental concern of the consuming society. In this respect, many prior art patents are directed toward methods of handling waste, particularly municipal waste with the purpose of reducing the amount of total waste targeted for landfill sites.
Conventionally, the first step of processing waste is to separate the compostable fraction of the waste from the non-compostable fraction.
U.S. Pat. No. 5,522,913 (Peguy) issued on Jun. 4, 1996, U.S. Pat. No. 5,441,552 (DeLillo) issued on Aug. 15, 1995 and U.S. Pat. No. 4,934,285 (Jormanainen) issued on Jun. 19, 1990 teach of sorting non-compostable material for recycling prior to subjecting the compostable waste fraction to composting. In International patent application WO 90/00162 (Stenroos et al.) published on Jan. 11, 1990, an apparatus for composting organic waste is described but it appears that the compostable fraction has already been separated from the non-compostable waste fraction.
In U.S. Pat. No. 5,556,445 granted to Mark K. Quinn et al., on Sep. 17, 1996 municipal waste is first heated to between 212xc2x0 F. and 500xc2x0 F. with steam. Then, compostable and non-compostable waste fractions are separated for additional treatment such as composting and recycling.
In U.S. Pat. No. 5,522,913, U.S. Pat. No. 5,441,552, U.S. Pat. No. 4,934,285, and International patent application WO 90/00162, the prior art is silent as to the safety of individuals handling the raw waste while sorting the compostable waste fraction from the non-compostable fraction. As well, there is a requirement of time and labour to accomplish this first step. In U.S. Pat. No. 5,556,445, the waste is sterilized by heat and steam making it safe for handling but the process of feeding the waste into the chamber is not continuous and the energy requirement render this process costly and inefficient.
Also, the prior art composting processes and installations usually produce unpleasant odors disturbing the neighbourhood.
An object of the present invention is therefore to eliminate the drawbacks of the prior art.
Another object of the present invention is to provide safe, economical, efficient and odor-free process and installation for transforming waste into usable products.
A further object of the present invention is to provide a waste composting process and installation capable of minimizing the waste fraction directed to landfill sites, and to reduce the toxicity of the waste fraction targeted for landfill sites by converting the organic matter present in the waste into compost.
More specifically, in accordance with the present invention, there is provided a process for composting waste containing organic matter, comprising the steps of feeding the waste to a bioreactor enclosed in a first closed building area, composting the organic matter in the bioreactor to produce a crude compost, maturing the crude compost in a second closed building area to produce a refined compost, creating a negative pressure in the first and second closed building areas by pumping air containing odorous substances from these first and second closed building areas, supplying the air containing odorous substances and pumped from the first and second building areas to a biofilter, extracting, by means of the biofilter, the odorous substances to produce substantially odor-free air, and releasing the substantially odor-free air to the atmosphere.
The present invention also relates to an installation for composting waste containing organic matter, comprising (a) a first closed building area, (b) a bioreactor for composting the organic matter to thereby produce a crude compost, the bioreactor being enclosed in the first building area, (c) means for feeding the waste to the bioreactor, (d) a second closed building area for maturing the crude compost to thereby produce a refined compost, (d) means for conveying the crude compost from the bioreactor to the second building area, (e) means for pumping air containing odorous substances from the first and second building areas to create a negative pressure in these first and second building areas, and (f) a biofilter supplied by the air pumped by the air pumping means and containing odorous substances, for extracting these odorous substances and for releasing substantially odor-free air to the atmosphere.
Since a negative pressure is maintained in the closed building areas, and the odorous substances are extracted from the pumped air by the biofilter, the process and installation according to the present invention produce compost without producing odors susceptible of affecting and disturbing the neighbourhood.
In accordance with a first preferred embodiment of the present invention, the air containing odorous substances and pumped from the first building area is first supplied to the second building area, and the air containing odorous substances and pumped from the second building area is supplied to the biofilter. More specifically, in accordance with the first preferred embodiment, the air containing odorous substances and pumped from the first building area is injected in the compost maturing in the second building area.
According to another preferred embodiment of the present invention:
the waste includes an organic compostable waste fraction formed by the above mentioned organic matter and a non-compostable waste fraction;
the bioreactor is supplied with both the organic compostable waste fraction and the non-compostable waste fraction;
the crude compost from the bioreactor is separated from the non-compostable waste fraction;
the installation further comprises a third closed waste receiving building area for receiving raw waste, a fourth closed building area in which recyclable material is sorted from the separated non-compostable waste fraction, a fifth closed building area in which the refined compost from the second building area is secondary refined, and a sixth closed building area in which the secondary refined compost is stored; and
a negative pressure is created in the third, fourth, fifth and sixth building areas by pumping air containing odorous substances from these third, fourth, fifth and sixth building areas, the air containing odorous substances and pumped from at least one of the first, third, fourth, fifth and sixth building areas is supplied to the second building area for example by injecting the pumped air in the compost maturing in the second building area, and the air containing odorous substances and pumped from the second building area is supplied to the biofilter.
The present invention further relates to a biofilter structure for extracting from air odorous substances produced by composting the organic matter, comprising a rock bed base, a network of perforated lines running into the rock bed base to inject in the biofilter the air containing the odorous substances, and a bed of filtering medium disposed on the top of the rock bed base for extracting the odorous substances from the air, this filtering medium consisting of an homogeneous mixture of wood chips, bark particles and organic material maintained at a predetermined degree of humidity.
Preferably, the organic material of the filtering medium is selected from the group consisting of compost, peat moss and a combination thereof.
The volumetric proportions of the filtering medium are as follows:
Finally, the predetermined degree of humidity is preferably located between 40% and 60%.
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non restrictive description of a preferred embodiment thereof, given by way of example only with reference to the accompanying drawings.